01 -
Preheat the oven to 350°F (175°C). Line a muffin pan with cupcake liners.
02 -
In a mixing bowl, cream together the butter and sugar using an electric mixer for 1-2 minutes until light and fluffy. Add the egg whites, sour cream, milk, and vanilla extract. Beat lightly to combine.
03 -
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry mixture to the wet ingredients a few spoonfuls at a time, mixing until just incorporated.
04 -
Add a small amount of light green food coloring until desired shade is achieved. Fill cupcake liners 1/2 to 3/4 full with batter.
05 -
Bake for 17-19 minutes or until a toothpick inserted in the center comes out with a few moist crumbs. Allow to cool completely before frosting.
06 -
In a mixing bowl, beat the butter with an electric mixer until smooth and creamy, about 2 minutes.
07 -
Add 2 cups of powdered sugar and watermelon Kool-Aid powder to the butter, beating until combined. Incorporate additional powdered sugar as needed, up to 2 more cups. Add a small amount of red food coloring to achieve a pink watermelon hue. Beat until smooth and well-blended.
08 -
Transfer the buttercream to a large piping bag fitted with a 1M Wilton piping tip. Pipe onto cooled cupcakes starting from the center, swirling outward and then back inward while building height.
09 -
Sprinkle mini chocolate chips on top of the frosting to represent watermelon seeds.